琥珀酰化提高大豆分离蛋白乳化性的研究

为了提高大豆分离蛋白(SPI)的乳化性,采用琥珀酸酐对大豆分离蛋白进行酰化改性。系统研究了SPI质量分数、琥珀酸酐用量和反应温度对大豆分离蛋白乳化性的影响,建立以上3因素与乳化活性和乳化稳定性关系的数学模型,并利用响应面法优化出大豆分离蛋白琥珀酰化的适宜条件:SPI质量分数6.5%、反应温度49℃、琥珀酸酐添加量11.5%。该条件下制备的琥珀酰化蛋白的乳化活性和乳化稳定性与未改性的大豆分离蛋白相比较,分别提高了2.98倍和4.86倍。     

超声波-酶法联合改性提高酸性条件下大豆分离蛋白的乳化性能

为了研究超声波联合酶技术提高大豆分离蛋白(Soybean Protein Isolated,SPI)在酸性条件下(pH 4)乳化性能的效果,本文以大豆分离蛋白为原料,以乳化性能和乳状液粒径为衡量指标,确定超声波联合植酸酶-酸性蛋白酶(Ultrasound combined with phytase-acidic protease,Uphy-aci)改性方法的最适宜条件。研究发现,当SPI浓度6%,植酸酶添加量4 U/g,酸性蛋白酶添加量1500U/g,植酸酶与酸性蛋白酶的酶解时间分别为50 min和30 min时,改性后的SPI(pH 4)乳化性能明显增加,乳状液粒度减小;通过表面疏水性(H0)和扫描电镜(SEM)分析了超声波-酶复合改性处理的SPI,发现在酸性条件下,SPI表面疏水性含量为487.78,比未改性提高了71.2%,并呈现破碎均一、多孔的微观结构。因此,超声波与植酸酶-酸性蛋白酶联合改性提高酸性条件下SPI的乳化特性等功能性质,并且拓宽了大豆分离蛋白的应用领域。     

大豆分离蛋白乳化性影响因素的研究

本文对影响大豆分离蛋白乳化性的外部因素进行了研究,实验证明大豆分离蛋白的乳化能力与蛋白质浓度、加热温度、pH值、NaCl浓度、卡拉胶浓度、搅拌时间密切相关。因此,在表征大豆蛋白的乳化特性及乳化稳定性(ESI)和乳化活性(EAI)时,应考虑这些因素。     

物理作用力对大豆分离蛋白乳化性及乳化稳定性的影响

研究物理作用力对4 种供试大豆分离蛋白乳化性及乳化稳定性的影响。分别采用不同浓度的NaCl、NaSCN、尿素和1,2- 丙二醇处理大豆分离蛋白以改变其物理作用力。研究结果表明：随着NaCl 和NaSCN 浓度的增加,乳化活性指数(EAI)值均呈先降低再升高的趋势,说明静电作用力起主导作用,疏水相互作用不利于乳化性。随着NaCl 和NaSCN 浓度的升高,乳化稳定性(ES)值均降低,说明静电作用力起主导作用,并且比疏水相互作用力的影响强。加入尿素可使蛋白质的疏水基团暴露出来,使EAI 值升高,但是加入不同浓度的尿素对乳化性的影响差别不大。EAI 值随着1,2- 丙二醇浓度的升高而升高,说明氢键相互作用利于乳化活性和乳化稳定性。     

酰化对大豆分离蛋白乳化性能的影响

目的:研究化学改性对大豆分离蛋白(SPI)乳化性能的影响;方法:采用乙酸酐和琥珀酸酐对SPI进行化学改性;结果:随酰化试剂用量的增大,酰化程度不断提高,在相同酰化试剂用量的条件下,乙酰化程度高于琥珀酰化.SPI的乳化活性指数(EAI)和乳化稳定性(ES)都随酰化程度的增大而增大.在中性和弱碱性(pH 5.0～9.0)范围内,酰化明显提高了SPI的EAI和ES.琥珀酰化的改性效果优于乙酰化;不过离子强度削弱了SPI的EAI和Es;结论:酰化可有效提高SPI的乳化性能,其中琥珀酰化的改性效果优于乙酰化.     

大豆分离蛋白溶解性和乳化性影响因素研究

研究了pH、大豆分离蛋白(SPI)质量浓度、NaCl浓度、搅拌时间和温度等因素对SPI溶解性和乳化性的影响.结果表明,0.8%的SPI在pH 6.0的条件下,实验浓度范围内的NaCI均使SPI溶解性和乳化性降低,适当的延长搅拌时间和升高温度可以显著提高SPI溶解性和乳化性.在室温条件下,搅拌50 min时SPI溶解度最...     

植物球蛋白/姜黄素纳米复合物的制备及其对O/W型Pickering乳液氧化稳定性影响

本论文以两类植物球蛋白:豌豆分离蛋白(PPI)和大豆分离蛋白(SPI)为材料制备荷载姜黄素蛋白纳米复合物,并探究荷载前后蛋白所制备乳液的物理和氧化稳定性差异。结果表明:PPI和SPI在pH 3.0和pH 7.0下荷载前后蛋白纳米颗粒粒径没有明显变化。pH 7.0时两蛋白姜黄素荷载量均高于pH 3.0,各pH下SPI荷载量要高于PPI。表面疏水性的显著降低与荧光淬灭现象发生表明形成两种蛋白纳米复合物的主要作用力为疏水相互作用,同时在两pH下,PPI比SPI荧光蓝移趋势更明显且有效淬灭常数也更大,即更易形成复合物。与原蛋白相比,荷载后各蛋白颗粒所制备乳液乳化活性有少许降低,同时pH 3.0时各蛋白颗粒乳化活性要高于pH 7.0。各乳液生成初级氧化产物脂质氢过氧化物浓度的变化趋势与生成次级氧化产物TBARS相类似,均为荷载姜黄素后各乳液氧化水平加速,同时pH 3.0时各类型乳液油滴氧化程度均高于pH 7.0。     

化学改性对大豆分离蛋白表面疏水性的影响

在以ANS(1-苯胺基-8-萘磺酸)荧光探针法测定大豆分离蛋白(SPI)表面疏水性的基础上,研究了化学改性对大豆分离蛋白表面疏水性的影响.用脲和SDS处理大豆分离蛋白,结果发现改性后的大豆分离蛋白表面疏水性明显提高;在pH 8.0、60℃、SDS浓度为25 g/L时,测定的表面疏水性指数S0最大.     

加工工艺对荞麦蛋白功能特性的影响

探讨了加工工艺对荞麦蛋白(BWP)功能特性的影响。pH＜5．0和 pH＞6．0时,喷雾干燥制备的荞麦蛋白(SBWP)的溶解度高于商品大豆分离蛋白(SPI)(P＜0．05)。pH＜7．0时,超声协助提取荞麦蛋白(U- BWP)的溶解度较搅拌提取荞麦蛋白(M-BWP)和脱脂、超声协助提取荞麦蛋白(DU-BWP)好；pH＞7．0时,结果相反。总体来说,BWP 持油能力较 SPI 强,且冷冻干燥制备的荞麦蛋白(F-BWP)的持水、持油能力强于 S-BWP (P＜0．05)。BWP 的乳化活性与其溶解度呈正相关。pH 4．0～5．0时,BWP 的乳化活性指数(EAI)最小而乳化稳定性(ES)最高。脱脂处理明显提高了 BWP 的 EAI 和 ES。     

超声处理对大豆分离蛋白溶解性和乳化活性的影响

采用超声波处理大豆分离蛋白,观察对其溶解性和乳化活性的影响。结果表明,超声处理时的温度和时间、NaCl浓度以及大豆分离蛋白浓度均会影响其溶解性和乳化活性。0.01g/mL的大豆分离蛋白溶液调节pH6.0,在室温(23～25℃)下采用500W超声功率处理5min时,其溶解度最大达1023μg/mL,是未超声处理(805.9μg/mL)的1.3倍,乳化活性达18.3mL/g,是未超声处理(11.9mL/g)的1.5倍。超声处理可以显著提高SPI的溶解性和乳化活性,这为拓宽其在食品工业中的应用提供了理论依据。     

葡聚糖接枝对大豆蛋白功能特性及结构的影响

采用干热糖基化对大豆分离蛋白进行改性,研究其功能特质及结构特性。以葡聚糖和大豆分离蛋白(soy protein isolate,SPI)为原料,考察底物质量比和反应时间两个因素。结果表明:蛋白质与糖质量比2∶1,反应温度60℃时,产物接枝比较高,褐变程度中等;与SPI相比,糖基化之后大豆蛋白的溶解度提高了72.72%,乳化活性(emulsifying activity,EAI)和乳化稳定性(emulsion stability,ESI)分别提高了117.53%和134.20%。十二烷基硫酸钠聚丙烯酰胺凝胶电泳(sodium dodecyl sulfate-polyacrylamide gel electrophoresis,SDS-PAGE)表明SPI与葡聚糖发生了糖基化反应;傅里叶红外光谱(Fourier transform infrared spectroscopy,FT-IR)和荧光光谱分析表明,糖链的引入导致了大豆蛋白空间结构的变化;模拟体外消化特性结果表明,葡聚糖糖基化修饰对SPI体外消化性的改善效果不明显。     

Emulsifying properties of proteins extracted from Australian canola meal

Canola protein albumin fraction, globulin fraction, and canola protein isolate (CPI) were compared to commercial soy protein isolate (SPI) in terms of their emulsifying properties at various pH values. The globulin fraction had higher emulsifying capacity (EC), higher emulsifying activity index (EAI), and the droplet size of emulsions it stabilized was consistently smaller irrespective of pH compared to albumin fraction or CPI. In comparison to SPI, globulin fractions also had higher EC at all pH values tested, higher EAI at acidic pH, and smaller or comparable average emulsion droplet size at both pH 4 and 7. The stability of canola protein based emulsions were comparable to those of SPI based emulsions at most pH values (except the emulsion stabilized by the CPI at pH 4), with no significant (p > 0.05) changes in droplet size during storage for up to 7 days at room temperature. These emulsions, however, experienced separation into the emulsion and serum phases after 24 h storage at room temperature with the exception of CPI- and SPI-stabilized emulsions at pH 9. This study demonstrates the comparable emulsifying properties (forming or stabilizing) of some canola proteins to commercially available SPI, suggesting the potential use of canola proteins in food applications.     

Emulsifying properties of canola and flaxseed protein isolates produced by isoelectric precipitation and salt extraction

The emulsifying (emulsion capacity, EC; emulsion activity/stability indices, EAI–ESI and creaming stability, CS) and physicochemical properties (surface charge/hydrophobicity, protein solubility, interfacial tension, and droplet size) of chickpea (ChPI), faba bean (FbPI), lentil (LPI), and pea (PPI) protein isolates produced by isoelectric precipitation and salt extraction were investigated relative to each other and a soy protein isolate (SPI). Both the legume source and method of isolate production showed significant effects on the emulsifying and physicochemical properties of the proteins tested. All legume proteins carried a net negative charge at neutral pH, and had surface hydrophobicity values ranging between 53.0 and 84.8 (H₀-ANS), with PPI showing the highest value. Isoelectric precipitation resulted in isolates with higher surface charge and solubility compared to those produced via salt extraction. The EC values ranged between 476 and 542 g oil/g protein with LPI showing the highest capacity. Isoelectric-precipitated ChPI and LPI had relatively high surface charges (~−22.3 mV) and formed emulsions with smaller droplet sizes (~ 1.6 μm), they also displayed high EAI (~ 46.2 m²/g), ESI (~ 84.9 min) and CS (98.6%) results, which were comparable to the SPI.     

大豆球蛋白-花青素Pickering乳液性质

制备大豆分离蛋白(soybean protein isolate,SPI)与花青素(anthocyanin,ACN)共价复合Pickering乳液。研究不同ACN体积分数下,共价复合颗粒的表面疏水性,Pickering乳液的乳化性与乳化稳定性、流变性质和微观结构。结果显示,当ACN体积分数由0%增加到0.15%时,共价复合颗粒的表面疏水性由18 174降低到8 945;Pickering乳液的乳化性增加了127 m2/g,乳化稳定性增加了近1倍;同时乳液脂滴状态得到了明显的改善。实验结果证明,乳液呈现类固体特性,表现出典型非牛顿假塑性行为。本研究还发现,随着ACN的添加,SPI-ACN共价复合Pickering乳液呈现出桥接乳液形态,这将为食品行业中开发新型Pickering乳液提供理论参考。     

Effects of homogenization on the molecular flexibility and emulsifying properties of soy protein isolate

The sensitivity of soy protein isolate (SPI) to trypsin was characterized by its flexibility. The effects of different homogenization conditions on soy protein isolate flexibility and emulsifying properties were investigated. Set the homogenization pressure was 120 MPa (megapascal) and the homogenous number of times is 0–4 times, the flexibility increases with the increase of the homogenization times (0–3 times), the change trend of flexibility is not obvious (3–4 times). When the homogenization times was 0–3 times, the emulsifying activity increases, and the emulsifying activity was the strongest at 3 times, after homogenization 3 times, the change trend of emulsifying activity is not obvious, the trend of emulsification stability and emulsification activity were similar. The surface hydrophobicity increases with the increase of homogenization times, while the turbidity decreases. The other structural indicators such as Ultraviolet scanning and endogenous tryptophan fluorescence spectroscopy suggest that the structure of SPI becomes more stretch as the flexibility increases.     

Emulsifying properties of soy protein isolates obtained by microfiltration

Soy protein isolate (SPI) fractions were produced using two different pore size microfiltration membranes. Microfiltration was carried out on SPI produced by isoelectric precipitation of a crude protein extract. Five fractions were obtained: two retentates and two permeates from the two membranes plus an intermediate fraction obtained as the retentate on the small‐pore‐size membrane using the permeate from the larger‐pore‐size membrane. Emulsions stabilised by the retentate fractions exhibited higher values (P < 0.01) of emulsion stability index (ESI) and emulsifying activity index (EAI) than those stabilised with fractions made from the permeates. The intermediate fraction gave intermediate ESI values, while the EAI values were not significantly different from those for SPI and one of the retentates. SDS‐PAGE profiles indicated that the fractions exhibiting high functionality in terms of ESI and EAI were also richer in 7S globulin soy protein subunits. © 2002 Society of Chemical Industry     

Food Protein Functionality in a Liquid System: A Comparison of Deamidated Wheat Protein with Dairy and Soy Proteins

ABSTRACT: Solubility, surface properties, overrun, foam stability, apparent viscosity, and emulsification properties were evaluated for 3% protein dispersions of deamidated wheat protein (DWP), sodium caseinate (SC), soy protein isolate (SPI), and whey protein isolate (WPI). DWP dispersion had the highest apparent viscosity, 25% higher emulsion activity index (EAI), and 82% higher emulsion stability index (ESI) when compared to SPI dispersions. Dispersions of DWP had similar foaming properties and surface properties when compared to SC, but had 50% higher EAI and 1000% greater ESI when compared to the 2 dairy proteins. The utilization of DWP could be expanded into liquid food systems currently using dairy proteins.     

Emulsifying properties of soy protein isolate fractions obtained by isoelectric precipitation

Soy protein isolate (SPI) fractions were produced by isoelectric precipitation based on results of isoelectric focusing carried out on the crude soy extract. The fractions were produced from crude protein extract (pH 9.0) sequentially and non‐sequentially at isoelectric points (pIs) of 5.6, 5.1 and 4.5. Emulsions stabilised by soy proteins with pIs between 5.6 and 5.1 had the highest (P < 0.01) emulsion stability index (ESI), while those stabilised with proteins having pIs between 5.1 and 4.5 resulted in the lowest ESI for sequentially precipitated fractions. Non‐sequential fractionation at pI 5.1 produced fractions with higher emulsifying activity index (EAI) than sequential fractionation. SDS‐PAGE profiles indicated that the fractions exhibiting high functionality in terms of ESI and EAI were also richer in 7S globulin protein subunits. © 2001 Society of Chemical Industry     

Physicochemical characteristics and functional properties of grape (Vitis vinifera L.) seeds protein

The amino acid composition, physicochemical and functional properties of grape (Vitis vinifera L.) seeds protein (GSP) were evaluated and compared with those of soybean protein isolate (SPI). Amino acid analyses of GSP revealed high levels of glutamic/glutamine, glycine and aspartic/asparagines. SDS‐PAGE analysis demonstrated that globulin was the major protein component in GSP, whose subunit molecular weights were mainly varied from 25.5 to 40.0 kDa. The isoelectric pH of GSP was found to be at the acidic pH of around 3.8. At all the pHs tested except pH 2.0, no significant changes of GSP secondary structure were observed. GSP exhibited beneficial functional properties such as preferable solubility and emulsifying activity, while the foaming properties and water holding capacity were relatively poor compared to SPI. It could then be employed to soup, sauce, beverage or meat product for improving nutritional and sensory quality of these foods at appropriate pHs.